­Emotion may be an important factor in determining who's most fit for leadership. Fred I. Greenstein, a professor of politics at Princeton University, wrote a book evaluating 11 American presidents on six leadership qualities, including cognitive style and emotional intelligence. Greenstein found that Eisenhower, Ford, and George H.W. Bush were free of emotional conflicts that could have hampered their leadership, while Johnson, Carter, Nixon and Clinton had emotional handicaps that affected their presidencies [source: Gailey]. In Greenstein's view, Reagan, Truman, Kennedy and FDR faced emotional undercurrents that did not affect their leadership [source: Gailey].

Alexithymia and Lack of Emotional Intelligence

In 1991, Canadian psychologist Robert Hare released a study indicating that psychopaths may have different brains from the rest of us [source: Nichols]. While psychopaths remain intellectually aware of society's rules, they lack emotional intelligence. The profile of a psychopath includes impulsivity, lofty goals without the discipline or focus to achieve them, a propensity for boredom, no close personal attachments and of course, a lack of empathy. When Hare monitored psychopaths' brain waves while they examined certain words, including those that bring up a host of emotions for most people, he found that there was no activity in the parts of the brain involved in emotion. Hare described these psychopaths as "emotionally color-blind" to Maclean's magazine in 1996 [source: Nichols].

Hare's work seems to indicate that psychopaths have abnormal brain functions in areas related to processing emotion and language -- meaning that there's a neurological rationale for some heinous crimes, as opposed to some environmental factor such as child abuse. If these psychopaths were to be tested for IQ, they would likely show up as normal, but it's in a lack of emotional intelligence that we see the disturbances in brain health.

If a person is on the low end of the emotional intelligence spectrum, he or she may have a condition known as alexithymia. Alexithymia is the inability to understand or express emotion. Because of what scientists know about emotions in the brain, they theorize that alexithymia may either relate to a malfunctioning in the right hemisphere or an overactive left hemisphere (leaving the right hemisphere unable to compensate) [source: Bermond et al.]. It's also possible that the corpus callosum, the part of the brain that governs communication between the right and left sides of the brain, is damaged to the point of blocking the messages regarding emotion [source: Becerra et al.].

­­Alexithymia sometimes manifests itself after a person suffers a brain injury such as blunt trauma. But the condition may eventually be able to tell us more about what happens during brain disorders absent of such trauma. For example, alexithymia has been linked to eating disorders, panic disorders and post-traumatic stress disorder [source: Becerra et al.]. The condition may also provide clues about autism spectrum disorders one day; one common theme of autism disorders is a lack of emotional connection, so that those with the disorder can't pick up on social cues. Decreased cerebellum activity has been linked to autism and Asperger's disorder [source: Bermond et al.].

For more on emotional intelligence, IQ and other brainy topics, take a look at the links on the next page.